The graphical user interface, as exemplified by Microsoft Windows and the Apple Macintosh, enables users to work with more than one application program at the same time. In addition, the individual applications may have the capability of supporting many task or document windows, generally designated by the term "multiple document interface" (or MDI).
In the case of the powerful word processing applications, such as Microsoft Word, WordPerfect, and FrameMaker, the capability of performing independent work in multiple documents is generally considered an essential element of their functionality. It simply means that users do not have to close one file (by writing it from the computer's memory to a permanent storage system) before opening another file (by performing the reverse operation). There are many benefits derived from this, among which are: (i) the ability to switch, or activate, open windows quickly and so work alternately among different documents; (ii) the ability to copy, cut and paste text, graphic images, or other document objects from one window to another; and (iii) the ability to make comparisons between documents and implement revisions among different documents in a flexible manner.
While the multiple document interface offers many advantages over earlier interfaces, such as that provided in DOS-based applications, the potential advantage of this additional functionality of the MDI has not been fully realized in the case of word processing applications for several reasons.
Even though the number of document windows that may be opened is only limited by the resources of the computer hardware and the ability of the operating system and application to utilize these resources; the usefulness of having more than a few document windows open at once is limited by the inability to organize or view them in a useful fashion. In fact, because overlapping windows obscure each other, users typically see and work with just one document window at a time. This window state is described as "maximized." To view another document window, users may select the chosen window from a list, and then view this one in the maximized state. An alternative for users is to use a "tile" command that proportional spaces the windows so that each one occupies an equal amount of the application's work space (or some other space allocation as determined by an algorithm). Although the user exposes all the windows by tiling, the visible area of each document is inevitably reduced so that, in effect, each document is partially hidden in the same way as it would be if the windows were partially overlapping.
Neither maximizing nor tiling is entirely satisfactory when users are working with many document windows. The inadequacy of each method increases in proportion to the number of windows that users have open. In the case of five, 10 or 15 document windows, users can continue to switch from one maximized window to another by means of a list, but it becomes increasingly difficult to identify the document that occupies each window from this list. If users choose to tile the windows, then the amount of space occupied by each window is generally insufficient to work in the document, as most of the text (even on a single line) will be hidden from view without users' having constantly to scroll the window vertically or horizontally.
There are ergonomic considerations concerning the multiple document interface that until now appear to have been overlooked or neglected by word processing applications that are widely used for desktop publishing. These relate to the "preferred" way in which users work with a document. The first consideration deals with the limitations on the utility of a "WYSIWYG" interface and second with the "natural way" to work with multiple documents.
A key feature of sophisticated word processors is a "WYSIWYG" ("what you see is what you get") interface. This means that users see a representation of the document on the computer screen that broadly corresponds in many details (though not all) with the document as it will appear when printed out. This WYSIWYG, or page layout, view of a document window is not necessarily the only view provided by the word processor or even the preferred view in which users work. For example, greater computer system resources are required in this view, and this can reduce the speed of the computer's response to user input as when scrolling and typing, etc.
It is for this reason that word processors typically offer alternative views in which users can work with a document. Among these are a draft, or text mode, and an outline mode. (The draft mode displays text in a monospaced font with virtually no details of the page layout. The outline mode displays the heading levels of a document with or without the text that constitutes the body of the document.) In addition, there is generally a "normal" view in which the text is displayed in the user-selected font(s) and some limited layout information is represented. The normal view represents a trade-off between optimizing use of computer system resources and the accurate representation of the document on the computer screen. This is, generally speaking, the preferred way in which users perform most word processing tasks.
There is a further limitation of the page layout view that is hard to overlook: the vast majority of computer monitors have a physical screen with a horizontal (or "landscape") orientation, whereas the vast majority of documents composed by users in word processing applications have a vertical (or "portrait") orientation, corresponding with the standard page sizes (book, letter, or legal, etc.) This anomaly means that the users with normal eyesight using normally sized computer monitors are unable to see a whole document page in a document window while continuing to compose the document. This is because the magnification of the document in the window has to be reduced to a percentage of frequently less than 50% for users to see a complete page. Since the normal size of a readable typeface is from 10 to 12 points (the range typically used in newspapers and magazines), at 50% magnification the effective point size is reduced to 5 or 6 points at the most. This is the kind of "small print" that is commonly associated with eyestrain in paper documents. On modern computer monitors of up to 17 inches with a Super VGA resolution of 1024 by 768 pixels a significantly better than average screen display type of this size is typically considered difficult or impossible to read. The result is even more exacerbated when the display is rendered on one of the many personal computer monitors of 14 inches many with only a VGA resolution of 640 by 480 pixels.
The WYSIWYG capabilities of sophisticated word processors are, therefore, often underutilized because of the impracticality of working with text of this size. A common and somewhat inconvenient method employed by users is to alternate between the normal and page layout view in the same document window. The utility of this solution decreases as the need to switch views increases. When users are performing detailed page layout work, the need to see the WYSIWYG view of the document on a constant basis becomes almost a necessity.
The second consideration is that work with multiple documents be performed in the "natural way". A general theme of the graphical user interface (and a particular implication of the term "desktop publishing") is the concept that, to a lesser or greater degree, personal computers enable users to work with applications that symbolically duplicate their real desktop environment in the virtual environment of the computer. In fact, it is a fundamental yardstick of a well-designed application that it should present users with a highly intuitive interface, meaning one that can be understood and used with the minimum requirement to learn to think in new and, at first, "unnatural" ways. The success of the Macintosh and of Windows is based on the simplicity of this "virtual desktop" metaphor.
In light of this, it can be inferred that the natural way to work with an application is one that most closely corresponds with the users' familiar environment of the "real desktop." This has very real applicability for word processing applications where almost the complete set of terms and concepts used by these programs has been acquired from the "real world" activities of preparing copy and art for layout and of performing typesetting and printing functions.
There is a particular aspect of the real desktop that appears to be overlooked or neglected by the virtual desktop of word processing applications. Users handling paper documents are likely to store them in a file cabinet; this in analogous with the file management system of the computer. The documents that users are currently working with are likely to be on their desktop; this is analogous with the open document windows in a word processor. Users may pile the current documents on top of each other or strew them across the desktop; this is analogous with the current document window being maximized and the remaining windows being hidden beneath it or with tiling all the document windows. However, users are likely to arrange the documents in some way that makes it fairly quick and easy for them to pick up the documents they need. This is where the analogy with word processing applications breaks down. In addition, when working with related documents, users may often want to place documents next to each other, and, in the case of making detailed comparisons between them, it is most likely users will want to place the documents side by side.
There may be a reason why it may be more natural to place documents side by side, rather than in another configuration, such as above and below or partially overlapping each other. The reason is that when documents are placed side by side, readers require less eye movement to scan between lines of text, which can be kept in parallel, and it also makes it far easier to keep their place in both documents. These factors have long been recognized by professional proofreaders, who invariably prefer to work with narrow columns of typeset material and will generally place the typeset material to one side of the original manuscript if a comparison is required.
The side-by-side placement of windows is an existing capability of some applications using the multiple document interface, such as the File Manager of Windows for Workgroups. The command that produces this result is usually called "Tile Vertically"; its action is to space equally along the horizontal plane of the application work space all document windows that are not minimized (reduced to their minimum size). For example, if there are two windows, each will occupy half the application work space; if there are five, each will occupy one-fifth of the work space. Unlike the present invention, such a command, even if available, is of little value in word processing applications because it gives users no control over which document windows to arrange and does not wrap the text in each window.